The invention relates generally to revetments such as seawalls and other structures intended to dissipate and absorb fluid wave energy.
The erosion of beaches, lake banks, river banks and the like by wave action, either natural or as the result of passing water craft, represents a serious and long-standing problem. In an effort to prevent such erosion, numerous structures have been devised which are intended to dissipate and absorb the wave energy before it strikes and erodes beaches, banks and other riparian structures. Flat-faced seawalls are an example of such prior art structures. However, such flat structures are relatively inefficient in dissipating wave energy and, as a result, are plagued by erosion both in front of and behind the wall.
When a wave strikes a flat seawall, much of the energy may be dissipated by splashing over the wall. Water collecting behind the seawall may create destructive hydrostatic forces and results in erosion of the material behind the wall when it runs back out to the sea. Moreover, turbulence at the base of the front of a flat wall results in a general erosion of the material in front of the wall, with particularly severe erosion immediately at the base of the wall. Such erosion at the wall base may undermine the structure leading to its ultimate failure.
In order to avoid the deficiencies of flat seawalls, rocks or other assisting structures are often used in front of such walls. Further, the formation of structures which present irregular surfaces to the waves has been attempted in an effort to dissipate the wave energy more efficiently. Exemplary of such structures are the subjects of U.S. Pat. No. 2,344,302, issued Mar. 14, 1944, to L. F. Harza; U.S. Pat. No. 3,210,944, issued Oct. 12, 1965, to H. R. Svee; and U.S. Pat. No. 3,456,446, issued July 22, 1969, to S. Kusatake. With particular reference to the Harza patent, it is noted that this reference suggests revetments presenting surfaces formed of an array of juxtaposed equilateral, three-sided pyramidal projections. It is said that the tortuous path which a wave must follow in rolling up and down this revetment dissipates energy and may prevent the wave from rolling as far up the revetment as it otherwise might. Revetments of the form suggested by Harza are somewhat more effective in mitigating erosion and undermining than a flat seawall, but still leave room for improvement in terms of wave energy dissipation efficiency.